1. Field of the Invention
The present invention relates generally to an intelligent alarm apparatus with a telephone interface, and more particularly to an alarm apparatus connected to a standard telephone network with operating power furnished by the telephone network, and including a programmable processor for analyzing input from alarm sensors and directing an alarm signal to a remote location programmed in the processor.
2. Description of Related Art
A number of alarm systems are currently in use in which an alarm sensor transmits a signal through the telephone network by means of an automatic calling unit to a remote location.
Prior art sensors require interfacing at a low impedance level. The alarm message from a sensor is routed in the form of a current signal to an alarm system control unit. Several sensors may be attached to the control unit, each at a separate input. Further, the supply voltage to the sensors is provided by the alarm system power supply. The control unit of the alarm system transfers a signal from an alarm sensor to an automatic calling unit, which subsequently transmits the alarm signal to an alarm control point.
In a conventional system, the alarm control unit requires a power supply and backup battery. In addition, the automatic calling unit requires a separate power supply with a backup battery. The batteries must be dimensioned so as to have a sufficient capacity, even when the current loads of the sensor loops are included. For minimized disturbance, the loop current levels are typically in the order of 5 to 10 mA. Consequently, small systems requiring only one or two sensors would be excessively complicated and costly to build.
Furthermore, the battery life is limited and a battery malfunction causes the majority of faults in an alarm system.